Such an apparatus is known from French patent publication FR-A-2 646 656. In this known apparatus, the dosing element is firmly connected with a rotation shaft, which, in a manner not explained in more detail, is connected with a drive. In the known apparatus, it is therefore possible very well that a portion space is not positioned completely above the discharge opening when a next coffee portion is desired. In that condition, it is possible very well that not the complete portion space is emptied and that when dosing a next coffee portion, the coffee remaining from the preceding dosing action is still discharged unintentionally. It may be clear that thus an undesired effect of the known apparatus is obtained, because an undesired amount of coffee is delivered.
Also FR-A-1 341 016 shows such an apparatus. In this known apparatus, the dosing element is driven by a motor, which, via a transmission, an eccentric, a connecting rod with a cam, and a gear wheel connected with the dosing element, each time brings the dosing element into a next position. In the known apparatus, the stroke made by the gear wheel and hence the dosing element is dependent on the time during which the cam engages the gear wheel, which time again is dependent on the stroke of the eccentric. Because the stroke of the eccentric is determined by the distance from the rotation shaft of the eccentric to the eccentric point, because the eccentric is motor-driven, and because the motor each time makes only one or several complete strokes, the dosing element will always round off a dosing step completely. The known apparatus, however, cannot function properly in case of manual operation. In fact, man is not capable of each time accurately determining when a stroke has been made completely and, therefore, the dosing step has been rounded off completely.